OBJECTIVE: To develop an in vitro predictive system to evaluate the response of human tumors to a broad spectrum of chemotherapeutic agents before a patient is scheduled to a particular therapeutic regimen by making use of the phenomenon of premature chromosome condensation (PCC). APPROACH: The approach is based on the fact that most of the cancer chemotherapeutic agents not only cause cell death but also induce chromosomal aberrations. The PCC method makes it possible to visualize chromosome damage in interphase cells or those cells that will not be able to enter mitosis because of the lethal effects of the treatment. Cells from human tumors treated in vivo or in vitro with a given drug will be fused with mitotic HeLa cells and the PCC of the tumor cells will be scored for aberrations. The data on chromosome aberrations and the clinical regression of the tumor will be compared to find any correlations.